Metabolism is a key step in eliminating xenobiotics from the body. Despite the fundamental importance of metabolism in determining the potency of contaminants and carcinogens, little is known about sex-specific differences in critical metabolic pathways. Differences between the sexes can be due to steroid hormone (gonadal) interactions or to differences in gene content (genomic interactions). We propose to investigate the effect of gonadal vs. genomic interactions on metabolism of a class of ubiquitous environmental contaminants (polycyclic aromatic hydrocarbons, PAHs) in a primary target organ for chemical carcinogenesis, the lung. The model compound will be naphthalene, the predominant PAH in environmental tobacco smoke and a byproduct of fossil fuel combustion. Human exposure to naphthalene is a concern as naphthalene was recently declared a likely human carcinogen. Naphthalene toxicity is of interest in the female population for 3 reasons: 1) women develop lung cancer earlier and after less cigarette exposure than men, 2) naphthalene causes lung tumors in female (but not male) mice and 3) data shows that female mice are more sensitive than male mice to naphthalene pulmonary toxicity. Sex-specific effects on metabolism and detoxification of naphthalene in the lung will be investigated in this proposal. Alterations in these systems may pre-dispose the lungs of females to increased airway epithelial injury and subsequent remodeling dependent on the stage of the reproductive cycle at which exposure occurs. The central hypothesis is that elevated susceptibility of females to metabolically activated compounds, such as naphthalene, is influenced primarily by gonadal hormones. The central hypothesis is addressed through two specific aims. These will determine if: 1) Female gonadal hormones regulate pulmonary metabolism of naphthalene and 2) Female-specific gene expression regulates pulmonary metabolism of naphthalene. We will use a multidisciplinary approach that combines morphology, site-specific quantitative gene expression, enzyme activity measures and proteomic approaches to define the effect of sex and steroid hormones on bioactivation of naphthalene. The proposed studies are relevant to diseases associated with pulmonary remodeling and PAH activation, such as lung cancer.